JPH10287772A - Carbon black for tire tread compound - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide carbon black which can give a rubber compound being satisfactory in the incompatible properties i.e., high abrasion resistance and low-level heat buildup and improved in tear properties (elongation properties) and processability. SOLUTION: This carbon black is one having basic properties: the nitrogen adsorption specific surface area (N2 SA) is above 140 m<2> /g to below 200 m<2> /g and a DBP oil absorption of above 110 ml/10 g to below 160 ml/100 g, wherein the rate of N2 SA to the iodine value (IA) (N2 SA/IA) has a value of 0.85-0.98 and the aggregate properties as measured by centrifugal analysis satisfy: (1) the most frequent mode (Dst) of a distribution curve of Stokes equivalent diameters is 70-90 nm, and (2) the ratio of the Dst to the half-width value (ΔD50 ) of a distribution curve (ΔD50 /Dst) of above 0.81 to below 1.30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention provides a rubber compound composition having significantly improved abrasion resistance, tearing properties (elongation properties) and processability useful for compounding a tire tread without deteriorating heat generation properties. It is intended to provide a carbon black which can be improved.

[0002]

2. Description of the Related Art Carbon black is produced by introducing raw material hydrocarbons into a high-temperature combustion gas in a furnace furnace under strictly controlled conditions, and is produced by pyrolysis. Since it has a unique property that properties such as tensile strength and wear resistance can be dramatically improved, it is widely used as a filler and reinforcing agent for various rubber products such as tires.

[0003] Carbon black for rubber compounding is characterized by its physicochemical properties, that is, the unit particle diameter, surface area per unit weight (specific surface area), degree of connection of particles (structure), etc., of the carbon black. Carbon black having various properties is selectively used depending on the required rubber composition because it greatly affects the performance.

A rubber composition used for a tread portion of a tire has excellent resistance to abrasion (abrasion resistance) caused by rotating at a high speed and coming into contact with a road surface, and at the same time, is generated by contact. The hysteresis property of the rubber composition due to repeated deformation is also an important factor.

[0005] The improvement of the wear resistance of the rubber composition in the tire tread portion leads to an increase in the life of the tire, particularly, the running distance, and therefore has a very great advantage for the durability of the tire.

[0006] In order to improve the abrasion resistance, carbon black has been developed in the direction of increasing the surface area (small particle diameter) and increasing the structure. However,
The demand for improved wear resistance has increased, and in order to respond to this demand, the activity of the carbon black surface has been improved (Japanese Patent Laid-Open No. 1-2756)
No. 43, JP-A-61-207452, JP-B-7-64
957) and the half width of the aggregate distribution evaluated by centrifugal sedimentation analysis is reduced (JP-A-6-9313).
No. 6, JP-A-63-264647, etc.).

[0007] When means for improving wear resistance by using carbon black for compounding a tire tread as described above is adopted, the heat resistance of the rubber composition is increased while the wear resistance is improved, and the tearing property (elongation property) is also increased. ) And the drawback that the performance such as workability is reduced. That is, abrasion resistance and heat generation are mutually contradictory characteristics that are mutually contradictory, and various techniques have been proposed to solve this.

The invention using carbon black having two peaks in the aggregate distribution (Japanese Patent Publication No. 6-868,
4-74242, JP-A-63-199748), an invention in which the void volume of an aggregate is specified (Japanese Patent Publication No. 6-37582).
No. 6-41540, No. 7-755),
An invention in which a pore distribution mode diameter between particles measured by a differential scanning calorimeter (DSC) is specified (Japanese Patent Laid-Open No. 4-32553).
5, JP-A-4-370126, JP-A-5-2555
No. 42), and the invention (JP-A-4-363344, JP-A-5-43740, JP-A-5-170973) which specifies the wavelength dependence of the absorbance of the diluted aqueous dispersion in the visible light region, etc. It is disclosed as a means and a method for achieving both performance and heat-generating performance. In addition, a measure by increasing the structure has been proposed (JP-A-6-136289).
issue).

[0009]

SUMMARY OF THE INVENTION For the purpose of achieving a balance between high abrasion resistance and low heat build-up, it is impossible to achieve both at the same time, and a compromise must be made to some extent. Although various means have been proposed, carbon black having a property capable of giving a compounded rubber composition having sufficient performance has not yet been found, and the present invention relates to these properties. In addition to the above, the object is to improve the tearability (elongation properties) and processability of the rubber composition.

[0010]

Means for Solving the Problems To solve the above-mentioned problems, the present inventors have studied the interaction between carbon black and a rubber matrix (as a result, mechanical properties such as abrasion resistance and tensile strength, rubber properties). Processability, viscoelastic properties, etc.), that is, returning to the origin of focusing on the bonding state, researching the relationship between this and carbon black and physicochemical properties, and as a result, rubber and carbon black The present invention has been accomplished by finding that by changing the ratio of the physical bond and the chemical bond in the bonding, it is possible to give a performance completely different from the performance of the conventional carbon black on the rubber matrix.

In the bonding between the carbon black and the rubber matrix, the physical bonding is derived from the structural properties of the carbon black, such as the specific surface area and the structure of the carbon black, and the chemical bonding is the surface state on the carbon black surface. In the present invention, while increasing the ratio of the former in the bond and reducing the bond by the latter, it has become possible to further improve the various properties of the compounded rubber composition more than before. Things.

In addition, conventionally, as the particle size of carbon black becomes smaller, the abrasion resistance improves. However, when the particle size exceeds a certain range (approximately 140 m ² / g in N ₂ SA), the carbon black is not contained in the rubber matrix. Dispersion became difficult, and the phenomenon that the effect due to the particle size did not appear as it was as the performance of the rubber composition was observed.However, in the present invention, the dispersion state of carbon black in the rubber matrix was also studied, The mode diameter (D) in the carbon black aggregate distribution evaluated by centrifugal sedimentation analysis
st) and the half value width (ΔD50), ΔD50 / Dst, is controlled to a specific range larger than that in the past, thereby improving the dispersion state. This has made it possible to improve wear, tear, and workability, and to suppress a decrease in heat build-up.

[0013] Namely, the present invention is basically the nitrogen adsorption specific surface area (N ₂ SA) of 200 meters ² / less g exceed 140 m ² / g, DBP oil absorption amount (DBP) is of less than 160 ml / 100 g exceed 110 ml / 100 g in carbon black having characteristics, 1) the ratio of the N ₂ SA and iodine adsorption (IA) (N ₂ SA / I
A) The value of A is 0.85 to 0.98, 2) The most frequent value (Dst) of the distribution curve of Stokes equivalent diameter in aggregate characteristics measured by centrifugal sedimentation analysis
Is from 70 to 90 nm, and the ratio (ΔD50 / Dst) of the half width (ΔD50) of the distribution curve to Dst is more than 0.81 and less than 1.30.

In these requirements, N ₂ SA and D
The fact that the BP is within the above-mentioned specific range is a basic property for maintaining a high level of abrasion resistance with respect to the compounded rubber composition.

[0015] Carbon black is formed by blending of grape tuft-like aggregates (also called aggregates, the smallest unit of dispersion in a rubber matrix) formed by the fusion of very small unit particles with each other. It is already known that it has a great influence on the performance of the composition, and the above-described invention of setting the morphological characteristics of the aggregate to a specific range in order to control the characteristics of the rubber composition has been proposed.

However, in the present invention, in addition to the above requirements, the most frequent value (Dst) of the aggregate distribution is set to 70.
９０90 nm, and the half width of the distribution with respect to Dst (Δ
D50) and (ΔD50 / Dst) are controlled to be larger than before, and the value of N ₂ SA / IA is set to 0.8.
An essential requirement is 5 to 0.98.

If N ₂ SA is less than 140 m ² / g, it is difficult to ensure sufficient abrasion resistance of the compounded rubber composition, which is not preferable. Conversely, if N ₂ SA exceeds 200 m ² / g. Are the aggregate properties (Dst value and Δ
Even if D50 / Dst) satisfies the range of the present invention, the dispersibility in the rubber matrix decreases, and as a result, the abrasion resistance tends to decrease, and in addition, the processability of the compounded rubber decreases. Therefore, the range is more than 140 m ² / g and 200 m ² / g. A more desirable range of N ₂ SA is in the range of 145 to 185 m ² / g.

The DBP characteristic is another basic characteristic of the present invention. When the amount is less than 110 ml / 100 g, sufficient abrasion resistance cannot be maintained, and when the amount exceeds 160 ml / 100 g, ordinary carbon black is used. If the compounding amount is used, the viscosity of the rubber composition increases, and the processability and the elongation characteristics are deteriorated. A more desirable range for DBP is 130-150 ml / 100 g.

The features of the present invention, in addition to the basic characteristics of the aforementioned 1) the ratio of the N ₂ SA and iodine adsorption (IA) (N ₂ SA / I
A) The value of A is 0.85 to 0.98, 2) The most frequent value (Dst) of the distribution curve of Stokes equivalent diameter in aggregate characteristics measured by centrifugal sedimentation analysis
Is 70 to 90 nm, and the ratio (ΔD50 / Dst) of the half width (ΔD50) of the distribution curve to Dst satisfies the two requirements of 0.81 to 1.30. When the Dst property satisfies these conditions, the wear resistance, tearing properties and workability can be significantly improved without lowering the heat generation properties of the tire tread compounded rubber composition.

In addition, by setting the ratio of the specific surface area (CTAB) of cetyltrimethylammonium bromide to IA to be in the range of 0.70 to 0.85, the desired properties as the carbon black for rubber compounding of the present invention can be obtained. Can be given.

Further, the value of ΔD50 / Dst is changed to N ₂ S
Numerical value calculated from the measured values of A, IA and DBP, that is, the following formula (1)

[Expression 2] 2.5 × (DBP) × (N ₂ SA) × 10 ⁻⁵ + 1.6 × (N ₂ SA / IA) −1.26... (1) By controlling to a value larger than the numerical value, more preferable characteristics can be obtained.

Each property of the carbon black described in the present invention is measured by the following methods.

(1) Nitrogen adsorption specific surface area (N ₂ SA) Measured according to ASTM D3037-88 and expressed as a specific surface area per unit weight m ² / g.

(2) Iodine adsorption amount (IA) It is measured in accordance with JIS K6221-1982 and is expressed in mg / g of iodine adsorption amount per unit weight.

(3) DBP oil absorption JIS K6221 (1982) 6.1.2. It is measured by the method described in Method A and is expressed in ml of dibutyl phthalate (DBP) absorbed per 100 g of carbon black.

(4) CTAB adsorption specific surface area Measured according to ASTM D3765-85, and expressed as a surface area per unit weight m ² / g.

(5) Method for analyzing carbon black aggregate size by centrifugal sedimentation analysis Measurement equipment Disk Centrifuge Photosedi
Mentometer (DCF) [Joyce Lobl, Model 4 (Mark I
V)] Measurement method In a 30% by volume methanol aqueous solution to which a slight amount of a surfactant was added, 0.05 to 0.1% of carbon black was added.
Sonicate to completely disperse. The rotation speed of a rotating disk into which 15 to 25 ml of distilled water was poured as a sedimentation liquid (spin liquid) was set to 8000 rpm, and the dispersion 0.0
Add 2 to 0.03 ml. The recorder is activated simultaneously with the addition of the dispersion, and the amount of carbon black aggregate passing through a set point near the outer periphery of the rotating disk by settling is optically measured, and the absorbance (frequency) is represented as a continuous curve against time. Record. The sedimentation time is converted into a Stokes equivalent diameter by the following Stokes general form, and a corresponding curve of the Stokes equivalent diameter of the aggregate and its frequency is obtained.

D = K / √t (2) In equation (2), d is the Stokes equivalent diameter (nm) of the carbon black aggregate passing through the optical measurement point of the rotating disk t minutes after the start of sedimentation. . The constant K is determined by measuring the amount, temperature and viscosity of the spin solution and the density difference from the carbon black (the true density of the carbon black is 1.86 g /
cm ³ ), and is a constant determined by the number of rotations of the rotating disk. In the measurement of the present invention, the K value is 26 when 17.5 ml of distilled water is used as a spin solution, the measurement temperature is 23.5 ° C., and the disk rotation speed is 8000 rpm.
1.75.

Definition of the mode diameter (Dst) In the curve of the Stokes equivalent diameter of the aggregate obtained by the above-described measurement operation, the Stokes equivalent that gives the most frequent (actually, the maximum absorbance because an optical measurement is performed). The diameter is defined as the mode diameter (Dst), and is defined as the average size of the carbon black aggregate.

Definition of Half Width (ΔD50) The absolute value of the difference between the large and small Stokes equivalent diameters at which 50% of the mode diameter (Dst) is obtained is defined as the aggregate half width (ΔD50, nm).

[0030]

EXAMPLES Examples of the present invention will be described in detail below in comparison with comparative examples, but it goes without saying that the scope of the present invention is not limited thereby.

Examples and Comparative Examples Run No. 1 was prepared using a carbon black production furnace (FIG. 1) having a structure substantially similar to that disclosed in Japanese Patent Application Laid-Open No. 4-264165 (applicant: Asahi Carbon Co., Ltd.). 1 to 13 carbon blacks were produced.

An oxygen-containing gas introduction cylinder (inner diameter 250 mmφ, length: 400 mm) having a rectifying plate 5 for rectifying the oxygen-containing gas introduced from the outer periphery of the furnace head into a combustible fluid introduction chamber (inner diameter 450 mmφ, length 400 mm) 2. A fuel introduction device is provided on the center axis of the cylinder 4 and the downstream side of the cylinder becomes a convergence chamber (upstream end inner diameter 370 mmφ, downstream end inner diameter 80 mmφ, convergence angle 5.3 °) 8 on the downstream side, and
At the downstream side of the convergence chamber 8, the four feed oil spray ports (10B-1, 10B-2, 10B-3, 10B) shown in FIG.
-4) has a feed oil inlet chamber 11 including feed oil spray ports (10A to 10D) forming four separate planes installed on the same plane, the downstream side of which is a reaction chamber 12 and a reaction stop A production furnace which is composed of a reaction continuation and cooling chamber (inner diameter 140 mmφ, length 2000 mm) 13 equipped with cold water injection sprayers (a to h) and entirely covered with refractories was used.

The fuel has a specific gravity of 0.8622 (15 ° C./4
C), and heavy oil having the properties shown in Table 1 was used as the raw material oil.

[Table 1] * 1 BMCI: Bureau of Mines Correlation Index * 2 IBP: Initial boiling point

Using the above-mentioned carbon black production furnace, SAF grade carbon black was produced under the operating conditions shown in Table 2. Note that potassium hydroxide was used for controlling the structure (aggregate).

Production Conditions of Example Carbon Black and Comparative Example Carbon Black The production conditions of carbon black described in Tables 2 and 3 are as follows. It is manufactured by adjusting conditions such as the total amount of introduced air, the amount of feed oil, the feed pressure and temperature of the feed oil, the position of the cooling water for stopping the reaction, and the amount of fuel introduced.

The production conditions will be described in more detail. The surface area (N ₂ SA) can be adjusted by changing the ratio between the amount of feed oil and the total amount of air introduced, thereby increasing the ratio of the amount of introduced air. This increases the surface area. 2
The ratio of the two surface area indices, N ₂ SA / IA, can be controlled by the reaction stop position after the carbon black generation reaction, that is, the time from when the feed oil is introduced into the furnace until it is cooled. This value is reduced by performing on the side (the time until the reaction is stopped). The carbon black of the present invention can obtain a carbon black suitable for the present invention by using operating conditions in which the reaction time from the feedstock introduction position (the most downstream side when using a plurality of planes) to the quenching position exceeds 30 ms. it can. Mode diameter (Dst) and ΔD of Stokes equivalent diameter in aggregate characteristics
It is an important point of the present invention to control 50 / Dst larger than before, but this control is based on the position of introduction of the base oil and the characteristics of the base oil (temperature, viscosity and pressure at the time of introduction).
Dst by lowering the temperature of the feedstock oil (increasing the viscosity).
Can be increased. ΔD50, which is an index of the aggregate distribution, can be controlled to a wider side by using a plurality of raw material introduction surfaces to be used or changing the introduction position of the alkali metal. The production conditions of the carbon blacks of the examples and the comparative carbon blacks according to the present invention are shown in Tables 2 to 4, and the physicochemical properties of the produced carbon blacks and the control carbon blacks are shown in Tables 5 to 7.

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

[0040]

[Table 5]

[0041]

[Table 6] * The underlined part is out of the range of the present invention.

[0042]

[Table 7] * The underlined part is a characteristic outside the scope of the present invention. A control example is Asahi # 90.

(Rubber Performance Test) In order to evaluate the performance of the carbon blacks shown in Tables 5 to 7, rubber compositions were prepared at the compounding ratios shown in Table 8, and the carbon properties were tested. The results are shown in Tables 9 to 11.

[0044]

[Table 8] MBTS: 2,2'-dibenzothiazyl disulfide IPPD: N-isopropyl-N-phenyl-P-phenylenediamine

[0045]

[Table 9]

[0046]

[Table 10]

[0047]

[Table 11] The control example is Asahi # 90.

The rubber properties of each compounded rubber composition were measured under the following test conditions. Rubber property test conditions 1) Vulcanization conditions of compounded rubber composition: 145 ° C, 30 minutes 2) Abrasion resistance test: A wear test was performed using a Lambourn abrasion tester at a slip ratio of 25% and 60%, and the following formula was used. It was represented by the calculated wear resistance index (Lambourn wear index). Abrasion resistance index = (S / T) × 100 S: Loss of wear of control specimen (Run No. 13) T: Loss of wear in test specimen 3) Loss tangent: Viscoelastic spectro manufactured by Iwamoto Seisakusho Co., Ltd. Using a meter (model VES-F-III), the loss tangent (tan δ) was measured under the following measurement conditions, and indicated by an index with respect to the control carbon black. Measurement conditions Frequency: 50 Hz Dynamic strain rate: ± 1% Measurement temperature: 25 ° C. Initial load: 160 g weight 4) Dispersibility September, 1969, Rubber World (No. 16)
Vol. 0, No. 6, pages 63-70 (author: HE Rail)
According to the method described in Sbach et al.), using a micrograph of the compounded rubber surface magnified 32 times, it was visually determined which rank of the standard sample classified into 10-1. The sample determined to be in the middle of the rank, for example, 7.5 in the case of the middle of 7 and 8, is displayed. 5) Other rubber properties: JIS K6300-1974
And K6301-1975.

[0049]

[Evaluation] From the results of the measurements (Tables 9 to 11) of the compositions in which the carbon blacks of Examples and Comparative Examples having the physicochemical properties shown in Tables 5 to 7 were mixed with rubber, the effects of the carbon black of the present invention were evaluated. explain. Run No. The carbon blacks of Nos. 1 to 5 are according to the present invention.
No. The carbon blacks of Nos. 6 to 12 are Run N, a comparative example that does not satisfy one or two of the specific requirements of the present invention.
o. 13 is a control carbon black (trade name Asahi # 90,
SAF grade carbon black, manufactured by Asahi Carbon Co., Ltd.). Run No. 6 is a comparative example in which DBP was lower than the lower limit of the present invention. 7 is a comparative example in which the upper limit is reversed. Run No. 8 is RunNo. 5
This is a comparative example having almost the same basic characteristics as that of Run No. 3, except that ΔD50 / Dst of the aggregate characteristics was lower than the lower limit of the range of the present invention. 9 is the upper limit of the surface area range, R
un No. Conversely, reference numeral 10 is an example in which the value is below the lower limit. Ru
n No. 11 is an example in which the characteristics similar to those of Example 1 were obtained, but the N ₂ SA / IA characteristics exceeded the upper limit of the range of the present invention. 12 also has N ₂ SA / IA
With the characteristic of, it deviates to the larger side and ΔD50 / Dst
This is a comparative example in which the characteristics of the above are also not satisfied. The evaluation for each of these characteristic items is as follows.

(1) Regarding elongation characteristics In each of the examples, the elongation characteristics are greatly improved as compared with the control black. In addition, Run No. 6 and 8 to 1
0 shows good elongation characteristics, but Run No.
In the case of Run No. 6, the DBP characteristic was low outside the range of the present invention, and the wear resistance index was low. In Nos. 8 to 10, the values of ΔD50 / Dst and N ₂ SA are out of the range of the present invention, and therefore, the characteristics of the wear resistance index, the loss tangent, and the Mooney viscosity are reduced. (2) Properties of Mooney Viscosity Run No. The Mooney viscosities of 7 and 11 are much higher than the control black, because the structure or surface area ratio is beyond the scope of the present invention. All the carbon blacks of the present invention show superior properties to the control black, and the effect of the present invention is clear. (3) Lambourn abrasion resistance characteristics 7 shows a very good numerical value of the wear resistance index, but an extreme decrease is observed in each of the elongation characteristics, Mooney viscosity and loss tangent characteristics. In comparison,
The examples of the present invention have very excellent abrasion resistance, and no decrease is observed in other physical properties. (4) Regarding loss tangent (tan δ) characteristics It is clear from Table 9 that the examples have extremely excellent wear resistance, elongation characteristics, and workability. Shows the same or better characteristics as the control black despite the fact that it is common. (5) Dispersibility All of the carbon blacks described in the examples show 7.5 or more in comparison with the standard dispersion photograph. Run No. 10
Shows almost the same dispersibility as the black of the present invention, but is significantly inferior in abrasion resistance.

[0051]

The carbon black of the present invention essentially has an aggregate with a high structure developed,
Since the particle size is small (large surface area), the wear resistance can be maintained at a high level. Further, the surface characteristics of carbon black (evaluated by the ratio of N ₂ SA / IA in the present invention)
Is controlled to be lower than usual, so that it is difficult for the carbon black surface to form a strong bond with the rubber matrix. Thereby, the hardness of the compounded rubber composition does not increase, and high elongation characteristics can be obtained. This results in a significant improvement in the tier in the tread rubber composition. Further, since it becomes difficult to form a strong chemical bond at the time of rubber compounding, the Mooney viscosity of the unvulcanized rubber composition is kept at a low state, and the processability is improved. Furthermore, this improved the kneadability of the rubber and the carbon black, and made it possible to greatly improve the dispersibility of the carbon black in the rubber matrix. By improving the dispersibility in rubber,
Further, it was possible to use carbon black having a small particle diameter. Providing a carbon black for compounding a rubber composition, which is capable of improving abrasion resistance and suppressing deterioration of heat build-up by synergizing these effects, is an important development for the rubber industry.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view of an apparatus according to an example of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbon black reaction apparatus 2 Flammable fluid introduction chamber 3 Oxygen-containing gas introduction pipe 4 Oxygen-containing gas introduction cylinder 5 Straightening plate 6 Fuel oil spray apparatus introduction pipe 8 Convergence chamber 10A Feed oil spray port 10B Feed oil spray port 10C Feed oil Spray port 10D Feed oil spray port 11 Feed oil introduction chamber 12 Reaction chamber 13 Reaction continuation and quenching chamber a Quenched water press-in spray apparatus b Quenched water press-in spray apparatus Equipment f Quenched water press-in spray device g Quenched water press-in spray device h Quenched water press-in spray device

Claims (3)

[Claims] 1. A nitrogen adsorption specific surface area (N ₂ SA) of 140
exceed m ² / g 200 meters below ² / g, DBP absorption (DB
P) exceeds 110 ml / 100 g and 160 ml / 100
In the carbon black having a fundamental property of less than g, 1) the ratio of the N ₂ SA and iodine adsorption _{(IA) (N 2 SA /} I
A) The value of A is 0.85 to 0.98, 2) The most frequent value (Dst) of the distribution curve of Stokes equivalent diameter in aggregate characteristics measured by centrifugal sedimentation analysis
Is from 70 to 90 nm, and the ratio (ΔD50 / Dst) of the half width (ΔD50) of the distribution curve to Dst is more than 0.81 and less than 1.30. 2. The ratio of the specific surface area (CTAB) of cetyltrimethylammonium bromide to IA (CTA)
The carbon black for compounding a tire tread according to claim 1, wherein (B / IA) is from 0.70 to 0.85. 3. The value of ΔD50 / Dst is given by the following formula (1): 2.5 × (DBP) × (N ₂ SA) × 10 ⁻⁵ + 1.6 × (N ₂ SA / IA) −1.26 3. The carbon black for compounding a tire tread according to claim 1, wherein the carbon black is equal to or larger than the value determined in (1).